6) Pick appropriate collection test tubes. This is also a good time to consult your more experienced colleagues, but a simple guideline is to divide the volume of silica that you used by four and pick test tubes that can accommodate this volume. (200 mL of silica 50 mL fractions) 7) Once you have selected a column, you need to plug the stopcock end so that the silica will not drain out. This is normally done with a small piece of cotton or glass wool and a long stick or glass rod 8) Mount the column in the hood -due to the large volumes of volatile solvents used and the health risks associated with dry silica gel, you should never run a column outside of the hood. Check to see that the column is perfectly vertical -crooked columns make separation more difficult 9)Close the stopcock and add a few inches of eluent 10) Add sand(dried and washed) to the column using a funnel. Your goal is to produce a thin layer of sand (no more than 1 cm)above the plug that will help prevent the silica from ending up in the collection flasks 11) Measure out the correct volume of silica. The safest way to do this is by volume in the hood. Silica gel has a density equal to 0.5 gmL so you can use an Erlenmeyer flask to measure it out(100 g= 200 mL). Don't fill the Erlenmeyer more than one third full of silica since you will be adding solvent to the flask as well 12)Make a slurry of the silica by adding at least 1.5 times the volume of solvent as silica you just measured out. Mix it thoroughly by swirling or stirring vigorously to remove all the air from the silica.(Air bubbles will compromise the effectiveness of the column. 13) Using a powder funnel, carefully and slowly pour the slurry into the column making sure not to disturb the layer of sand. Stop pouring frequently to swirl the slurry so that the silica is evenly mixed. Once you've finished pouring, rinse the Erlenmeyer several times with the eluent and add the remaining solvent /silica mixture to the column 14)Using a pipet and eluent, rinse any silica stuck to the sides of the top of the column into the solvent layer6) Pick appropriate collection test tubes. This is also a good time to consult your more experienced colleagues, but a simple guideline is to divide the volume of silica that you used by four and pick test tubes that can accommodate this volume. (200 mL of silica = 50 mL fractions) 7) Once you have selected a column, you need to plug the stopcock end so that the silica will not drain out. This is normally done with a small piece of cotton or glass wool and a long stick or glass rod. 8) Mount the column in the hood - due to the large volumes of volatile solvents used and the health risks associated with dry silica gel, you should never run a column outside of the hood. Check to see that the column is perfectly vertical - crooked columns make separation more difficult. 9) Close the stopcock and add a few inches of eluent. 10) Add sand (dried and washed) to the column using a funnel. Your goal is to produce a thin layer of sand (no more than 1 cm) above the plug that will help prevent the silica from ending up in the collection flasks. 11) Measure out the correct volume of silica. The safest way to do this is by volume in the hood. Silica gel has a density equal to 0.5 g/mL so you can use an Erlenmeyer flask to measure it out (100 g = 200 mL). Don't fill the Erlenmeyer more than one third full of silica since you will be adding solvent to the flask as well. 12) Make a slurry of the silica by adding at least 1.5 times the volume of solvent as silica you just measured out. Mix it thoroughly by swirling or stirring vigorously to remove all the air from the silica. (Air bubbles will compromise the effectiveness of the column.) 13) Using a powder funnel, carefully and slowly pour the slurry into the column making sure not to disturb the layer of sand. Stop pouring frequently to swirl the slurry so that the silica is evenly mixed. Once you've finished pouring, rinse the Erlenmeyer several times with the eluent and add the remaining solvent/silica mixture to the column. 14) Using a pipet and eluent, rinse any silica stuck to the sides of the top of the column into the solvent layer. 65